Eucalyptus Leaf Beetle Research Articles

Oxidizable Phenolic Concentrations Do Not Affect Development and Survival of Paropsis Atomaria Larvae Eating Eucalyptus Foliage

Insect folivores can cause extensive damage to plants. However, different plant species, and even individuals within species, can differ in their susceptibility to insect attack. Polyphenols that readily oxidize have recently gained attention as potential defenses against insect folivores. We tested the hypothesis that variation in oxidizable phenolic concentrations in Eucalyptus foliage influences feeding and survival of Paropsis atomaria (Eucalyptus leaf beetle) larvae. First we demonstrated that oxidizable phenolic concentrations vary both within and between Eucalyptus species, ranging from 0 to 61mg.g-1 DM (0 to 81% of total phenolics), in 175 samples representing 13 Eucalyptus species. Foliage from six individuals from each of ten species of Eucalyptus were then offered to batches of newly hatched P. atomaria larvae, and feeding, instar progression and mortality of the first and second instar larvae were recorded. Although feeding and survival parameters differed dramatically between individual plants, they were not influenced by the oxidizable phenolic concentration of leaves, suggesting that P. atomaria larvae may have effective mechanisms to deal with oxidizable phenolics. Larvae feeding on plants with higher nitrogen (N) concentrations had higher survival rates and reached third instar earlier, but N concentrations did not explain most of the variation in feeding and survival. The cause of variation in eucalypt herbivory by P. atomaria larvae is therefore still unknown, although oxidizable phenolics could potentially defend eucalypt foliage against other insect herbivores.

Eradication of Paropsisterna beata (Newman) (Coleoptera: Chrysomelidae) in a semi-rural suburb in New Zealand

A large population of Paropsisterna beata (eucalyptus leaf beetle) was detected on Eucalyptus nitens (H. Deane & Maiden) Maiden (Myrtaceae) at Whitemans Valley, a suburb east of Upper Hutt, Wellington, in 2012. The suburb is a semi-rural residential area with a large number of eucalypt, planted for amenity, shelterbelt and firewood. Surveillance to delimit spread showed that the beetle population was confined to about 0.7 ha consisting of about 40 eucalypts. The Ministry for Primary Industries (MPI) initiated a response to eradicate the beetle population. Aerial applications of Dominex EC 100 (alpha-cypermethrin) and ground applications of Talstar (bifenthrin) respectively over a 15-month period targeted the adults and larvae in the foliage and the pre-pupae, larvae and emerging adults in the leaf litter. Removal of overwintering habitat by stripping loose bark from host trees further reduced the beetle population. Following these treatments, the beetle has not been detected through a series of surveys using light traps, bark inspection, sticky tapes, visual inspection from the ground, climbing and felling host trees for inspection for 2 years since the last detection of two adults on neighbouring trees. The P. beata population has been successfully eradicated using a combination of aerial and ground-based application of insecticides. The use of precision aerial applications (spot-spraying) has provided an additional tool for incursion response.

Two new species of Chrysomelobia Regenfuss, 1968 (Acariformes: Podapolipidae) from Paropsis charybdis Stål (Coleoptera: Chrysomelidae)

Two new species of Chrysomelobia Regenfuss, 1968, C. alleni n. sp. and C. intrusus n. sp., are described from Tasmanian specimens of the eucalyptus leaf beetle Paropsis charybdis Stål. This beetle is now known to host three species of Chrysomelobia, the other being Chrysomelobia pagurus Seeman, 2008, which is recorded from Tasmania for the first time. Thus, the three species of Paropsis Olivier known to have podapolipid mites each have three mite species from three separate lineages of Chrysomelobia. Collections of P. charybdis in New Zealand (n=150), where it is an invasive pest species, failed to locate any infested beetles, suggesting that these populations were established by uninfested beetles. The prospect of using these mites as biocontrol agents is discussed.

Biology of theEucalyptusleaf beetleParopsisterna selmani(Chrysomelidae: Paropsini): a new pest ofEucalyptusspecies (Myrtaceae) in Ireland

The biology of the Eucalyptus leaf beetle Paropsisterna selmani (de Little) (Chrysomelidae: Paropsini) was assessed in the field and under laboratory conditions. The invasive species, most probably from Tasmania, severely defoliates the new flush foliage of several Eucalyptus species in Ireland. 2 The adult beetles and larvae both fed on the foliage and caused typical broom-top damage to trees. Adult beetles over-wintered in the soil and emerged in April and laid egg batches ofapproximately seven eggs on the leaves. Teneral adults were most noticeable in late June and July. 3 In bioassays, the life cycle took approximately 26days to complete at 20 ◦ C, and survival rates were approximately 67% when fed on E. parvula. Teneral adults took 13.3days to initiate egg-laying. Leaf consumption was highest in female larvae, and adult beetles consumed a leaf area of approximately 102mm 2 /day. 4 A mean daily egg-laying rate of 11.4eggs/female was recorded over a period of 130days. This egg-laying rate is comparable to other leaf beetles attaining pest status in other Eucalyptus-growing regions. 5 The biology of Pt. selmani suggests that this will be a significant pest of Eucalyptus species grown for cut-foliage and forestry in Ireland. It also poses a potential threat to eucalypt-growing regions in the U.K. and mainland Europe.

Parobia husbandi gen. n., sp. n. (Acari: Podapolipidae): subelytral parasites of paropsine beetles (Coleoptera: Chrysomelidae)

Abstract Parobia husbandi gen. n., sp. n. is described from material collected from the subelytra of the southern eucalyptus leaf beetle, Chrysophtharta agricola (Chapuis), in Tasmania, Australia. Parobia gen. n. is distinguished from other podapolipid genera adult males and females with four pairs of legs and no setae on genua I−IV and femora III−IV, adult females with setae v1 and sc2 < 20 µm, and at least two pairs of coxal setae peg‐like, adult males with dorso‐terminal genitalia, dorsal shields C‐D‐E fused, and physogastric larval females with plates C and D entire. A series of morphological plesiomorphies and biological apomorphies link Parobia gen. n. with Chrysomelobia Regenfuss, the most basal genus of Podapolipidae.

Inundative release of coccinellid beetles into eucalypt plantations for biological control of chrysomelid leaf beetles

Abstract 1 Inundative augmentative releases of adult coccinellid beetles were assessed for their potential to effectively supplement biological control of outbreak populations of the Eucalyptus leaf beetle Chrysophtharta bimaculata in Eucalyptus nitens plantations.2 Mixed groups of two species of overwintering coccinellids, Cleobora mellyi and Harmonia conformis, were collected from the field then fed three diets in the laboratory prior to release. Both species were released in the summer into two E. nitens plantations with economically damaging Chrysophtharta populations.3 Differences between dispersal of coccinellids fed the three diets were slight; beetles brought straight out of overwintering before release were initially slower moving onto trees.4 Numbers of coccinellids on trees in monitoring plots decreased exponentially with time, and populations had returned to prerelease levels 7 days after release. The number of coccinellids recaptured decreased with increasing distance from the release point with very few coccinellids per tree at 70 m distance. Dispersal of C. mellyi away from the release plot was slower than that of H. conformis.5 Numbers of coccinellids on trees were significantly related to predation levels of C. bimaculata with a large decrease in the C. bimaculata population to below the economic damage threshold in plots where the numbers of coccinellids were high.6 The results of this study suggest that inundative release of laboratory reared coccinellids is possible for biological control of C. bimaculata, although it may only be economically viable in small, environmentally sensitive areas.

Role of foliar chemistry versus leaf‐tip morphology in egg‐batch placement by Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae)

Abstract The Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata (Olivier) (Chrysomelidae: Paropsini), deposits batches of eggs on the leaf surfaces of its Eucalyptus hosts. Using a primary host of the beetle, Eucalyptus regnans, the aim of the present study was to examine whether oviposition site discrimination was occurring at the level of the individual leaf and what, if any, chemical attributes were involved in site selection. From field surveys, it was found that 55−65% of egg batches were laid in the leaf‐tip zone, despite this zone representing only 5.6% of the total leaf‐surface area. Chemical analyses of expanding leaves showed that the concentrations of three essential oil components and three surface waxes varied significantly between the leaf tip and remainder of the leaf. However, on plastic mimic leaves with uniform, non‐foliar chemistry, eggs were still preferentially laid near ‘leaf’ tips. Hence, leaf essential oils and surface waxes need not be involved in oviposition site choice. Observations of ovipositing beetles showed that they wrapped their tarsi around the leaf margin, suggesting that the ability to grasp the edges of a leaf may explain the oviposition pattern observed.

Comparison of feeding efficiency, development time and survival of Tasmanian eucalyptus leaf beetle larvae Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) on two hosts

AbstractThe native Eucalyptus leaf beetle Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) has become a pest of the introduced, plantation species, Eucalyptus nitens Maiden in Tasmania, Australia. However, in the field it prefers to oviposit on the Tasmanian native species, E. regnans F. Muell. This laboratory study found that the performance of C. bimaculata larvae was superior on foliage of E. nitens compared with E. regnans. Larval development was 4 days shorter on E. nitens than on E. regnans foliage. Total food consumption per larva and relative consumption rates were about 30% lower while relative growth rates and weight of emergent adults were more than 25% higher on E. nitens than E. regnans. Efficiency of conversion (ECI) of fresh food into larval wet weight was 0.26 on E. nitens compared with 0.14 on E. regnans. Mortality of larvae feeding on E. nitens (23%) was only one third of that on E. regnans (69%), a result of high first instar mortality on E. regnans. Although the amount of foliage consumed per larva was lower on E. nitens (0.23 g vs 0.32 g), the differential mortality meant that the amount of E. nitens consumed per egg batch was 60% more than that of E. regnans. If these results occurred in the field, then the same monitored population of C. bimaculata eggs may result in heavier defoliation of plantation E. nitens than of E. regnans. These data show that the reported oviposition preference of C. bimaculata for E. regnans in the field cannot be explained by selection of host factors related to superior larval performance.

Calculating food consumption in the laboratory: A formula to adjust for natural weight loss

AbstractWe derive a formula for correcting the weight of food eaten by an animal for natural weight loss (or gain) of the food, such as through moisture loss and food respiration. The formula is derived using a differential equation to model the loss in fresh weight based on a constant consumption rate and assumptions about the form of the function for weight loss over time of the aliquot. The standard formula is shown to over‐estimate the weight of eaten food compared to our theoretically derived formula. This over‐estimation is negligible (< 0.2%) for moisture loss below about 10% but increases sharply to 8% when moisture loss is 50%. We illustrate the application of these two formulae using a laboratory study of consumption rate by larvae of a phytophagous insect: the Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae).

The application of generalized linear mixed models to multi-level sampling for insect population monitoring

Iwao's quadratic regression or Taylor's Power Law (TPL) are commonly used to model the variance as a function of the mean for sample counts of insect populations which exhibit spatial aggregation. The modeled variance and distribution of the mean are typically used in pest management programs to decide if the population is above the action threshold in any management unit (MU) (e.g., orchard, forest compartment). For nested or multi-level sampling the usual two-stage modeling procedure first obtains the sample variance for each MU and sampling level using ANOVA and then fits a regression of variance on the mean for each level using either Iwao or TPL variance models. Here this approach is compared to the single-stage procedure of fitting a generalized linear mixed model (GLMM) directly to the count data with both approaches demonstrated using 2-level sampling. GLMMs and additive GLMMs (AGLMMs) with conditional Poisson variance function as well as the extension to the negative binomial are described. Generalization to more than two sampling levels is outlined. Formulae for calculating optimal relative sample sizes (ORSS) and the operating characteristic curve for the control decision are given for each model. The ORSS are independent of the mean in the case of the AGLMMs. The application described is estimation of the variance of the mean number of leaves per shoot occupied by immature stages of a defoliator of eucalypts, the Tasmanian Eucalyptus leaf beetle, based on a sample of trees within plots from each forest compartment. Historical population monitoring data were fitted using the above approaches.

Bacillus thuringiensis var. tenebrionis shows no toxicity to the predator Chauliognathus lugubris (F.) (Coleoptera: Cantharidae)

Laboratory trials examined the effect of the bioinsecticide Novodor® (active ingredient 3%Bacillus thuringiensis var. tenebrionis (w/w) (Btt)), on the Australian plague soldier beetle, Chauliognathus lugubris, a predator of the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata. Spraying of C. lugubris and the C. bimaculata eggs supplied as food showed that neither Novodor® FC with active nor inactive Btt caused any decrease in predatory performance, longevity or fecundity of C. lugubris during the period of their population peak (December). Towards the end of their peak population levels, in late January, there was a steady increase in mortality which was not related to either of the Novodor® FC treatments. On average, male:female pairs of C. lugubris laid one egg batch and ate 30 C. bimaculata eggs a week whether untreated or sprayed with either Novodor® FC. This Btt‐based insecticide appears to be a suitable component of an integrated pest management (IPM) regime that aims to conserve natural predators.

Life History of Chauliognathus lugubris (F.) (Coleoptera: Cantharidae) in Tasmanian Forests

ABSTRACTAspects of the life history of Chauliognathus lugubris, a predator of eggs and early stage larvae of the Eucalyptus leafbeetle, Chrysophtharta bimaculata, were studied in southern Tasmania. In the laboratory (ambient temperature 15‐25°and artificial diet), the egg to adult period was about 10 months with seven larval stages. Advanced larvae (5th‐7th instar) were collected in the field from soil litter during mid‐winter. Adults were most common in the spring and early summer. with regular field collections suggesting adult longevity of 2‐3 months. Based on the pattern of ovarian development of field‐caught adults, in combination with the long larval development times, it appeared that C. lugubris has only one generation a year.

Genetic variation in Eucalyptus regnans and Eucalyptus nitens for levels of observed defoliation caused by the Eucalyptus leaf beetle, Chrysophtharta bimaculata Olivier, in Tasmania

Chrysophtharta bimaculata, a leaf eating beetle, is the major insect defoliator of Eucalyptus regnans and Eucalyptus nitens plantations in Tasmania. Little is known about variability in host susceptibility. Levels of defoliation in E. regnans and E. nitens progeny trials were examined using a four point visual scoring technique. Large family differences were found in observed defoliation levels with heritabilities of around 0.3 for E. regnans and 0.4 for E. nitens. Differences between families in levels of defoliation were repeatable across seasons in E. regnans and the level of defoliation in both species was highly and favourably genetically correlated with growth prior to defoliation ( r G around 0.8). Families which were initially growing faster suffered less observed defoliation, indicating that selection for rapid growth would indirectly lead to a reduction in defoliation levels. However, as level of defoliation was strongly genetically correlated with subsequent growth rate, later estimates of heritabilities for growth would be inflated by defoliation effects.

Modelling the impact of defoliation by the leaf beetle, Chrysophtharta bimaculata (Coleoptera: Chrysomelidae), on height growth of Eucalyptus regnans

A model of the effect of defoliation by the Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata Olivier, on the height growth of Eucalyptus regnans F. Muell. in young plantations is described. Two separate artificial defoliation trials were set up to provide data to calibrate and test the model. The treatments involved combinations of different defoliation levels and timing with and without a repeat of these treatments in the following year as well as a treatment involving regular removal of refoliating shoots (disbudding). The effect of disbudding was found to be greater on growth than was low levels of defoliation. The model gave an adequate fit to the data, but not all combinations of treatments were available to calibrate and test the model. A small simulation study employing the model to investigate the effect of defoliation and disbudding on plantation economics indicated a potentially high benefit to cost ratio for control of C. bimaculata, especially where refoliating shoots were grazed.

Regulation and usage of insecticides in Australian forestry from the mid-1960s to 1990

Summary Since the mid-1960s, 28 insecticide sprays or dusts, five fumigants (aluminium phosphide, dazomet, methyl bromide, naphthalene and p-dichlorobenzene) and one microbial insecticide (Bacillus thuringiensis) have been used, mostly in small quantities, by Australian forest services for control of indigenous and accidentally introduced insect pests in native forests, eucalypt or pine plantations, forest nurseries, and wooden structures. All of the applied insecticides have been officially registered for agricultural purposes (which include forestry applications) in each State/Territory under the provisions of a specific Act of Parliament. Until July 1989, the registration of insecticides by State/Territory authorities was subject to stringent evaluation and clearance by the Technical Committee on Agricultural Chemicals, a central authority responsible to the Co-ordinating Committee on Agricultural Chemicals, and through it to the Australian Agricultural Council. Since then, evaluation and clearance for registration has been the function of the Australian Agricultural and Veterinary Chemicals Council with direct responsibility to the Federal Minister for Primary Industries and Energy. This Council, established under the Commonwealth Agricultural and Veterinary Chemicals Act (1988), aims to ensure uniformity of assessment and registration of insecticides throughout Australia. In each State, special permits may be issued to allow insecticides to be used for purposes not covered by the registered product label or unregistered insecticides to be used in research trials. Additional legislation in the form of Acts of State Parliament, and Associated Regulations, governs the distribution, application and safe handling of registered insecticides. Most forest authorities now record insecticide purchases and consumption, and all have issued detailed instructions to their staff on spray preparation, storage, disposal, safe transport, spillage, accidental poisoning, loss or theft. The most extensive use of insecticides has been against the indigenous Spur-legged Stick Insect, Didymuria violescens (Phasmatidae), in Victorian ash-type eucalypt forests by aerial spraying with malathion, and for eradication of the accidentally introduced West Indian Drywood Termite, Cryptotermes brevis (Kalotermitidae), in south-eastern Queensland and New South Wales, by fumigating entire buildings and furniture with methyl bromide. In Tasmania, extensive aerial applications of synthetic pyrethroids have been carried out by APPM Forest Products to safeguard young plantations of principally Eucalyptus nitens (Shining Gum) from defoliation by the Tasmanian Eucalyptus Leaf Beetle, Chrysophtharta bimaculata. Outbreaks of all these pests cause serious economic damage when left unchecked. A sustained media campaign critical of pesticide usage in Australia has induced a much greater public awareness of the likely health risks posed by insecticides. Forest services are now committed to limit the use of insecticides and to promote biological and silvicultural techniques as alternative controls. Using insect resistant genotypes in eucalypt plantation programs is also expected to relieve insect pest problems in the future. However, insecticide applications are likely to remain front-line options for eradicating exotic insect pests of high destructive potential and for controlling large outbreaks of indigenous pests in commercial eucalypt plantations or in forest nurseries.

STAGE‐SPECIFIC MORTALITY IN TWO FIELD POPULATIONS OF IMMATURE CHRYSOPHTHARTA BIMACULATA (OLIVIER) (COLEOPTERA: CHRYSOMELIDAE)

AbstractA population census of the immature stages of 2 widely separated field populations of the Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata was conducted to determine the level of mortality occurring in each stage. Analysis of census figures for stage specific mortality showed that the egg stage was the most vulnerable with mortality ranging from 66% to 84%. Total mortality of the immature stages up to fourth instar larvae ranged from 95 to 97%. Similar mortality factors were seen to operate in each of the 2 populations with the greatest single factor being predation by coccinellids. The implications of this level and timing of natural biological control are discussed in relation to control strategies for C. bimaculata.

LIFE‐CYCLE AND ASPECTS OF THE BIOLOGY OF TASMANIAN EUCALYPTUS LEAF BEETLE, CHRYSOPHTHARTA BIMACULATA (OLIVIER) (COLEOPTERA: CHRYSOMELIDAE).

AbstractThe Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata, previously considered to be bivoltine, was found to have a univoltine life‐cycle in north‐west Tasmania. Field sex ratio and laboratory fecundity of the species were determined. Foliage of hosts within the series Obliquae (subgenus Monocalyptus) appeared to be the favoured food of C. bimaculata larvae. Four species of Obliquae tested were approximately equally favorable, and signficantly more favorable than foliage of a species of Piperitae (Monocalyptus).